Problem: If $9a + 5b = -10$ and $4x + 6y = -2$, what is $-35b + 20x + 30y - 63a$ ?
$= -63a - 35b + 20x + 30y$ $= (-7) \cdot (9a + 5b) + (5) \cdot (4x + 6y)$ $= (-7) \cdot (-10) + (5) \cdot (-2)$ $= 70 - 10$ $= 60$